The developing brain is a particularly vulnerable target for lead with developmental lead exposure resulting in cognitive and motor deficits that persist into adulthood. Although the effects of lead on the developing brain have been studied for decades, there are gaps in our understanding of how genetic background and environment may modify lead's influences on nervous system development and function. Different environmental milieus may have powerful effects on the response of the brain to lead. For example, environmental enrichment could have potential neuroprotective effects against developmental exposure to lead whereas an impoverished environment may exacerbate the neurotoxicity. In addition to environment, genetic background may also modify the outcome from developmental lead exposure, although at this point, this has not been examined systematically. Thus, our proposed research has the following specific aims: Specific Aim 1. Examine the influence of genetic background on lead induced behavioral and molecular deficits in the hippocampus. Using gene expression arrays and bioinformatics, we will first survey the normal developmental gene expression profile for the hippocampus, a structure known to be sensitive to developmental lead toxicity in 4 strains of rats typically used for neuroscience or toxicology studies. We then will examine changes in these expression profiles following developmental lead exposure. We hypothesize that rats of different genetic backgrounds will have different behavioral and gene expression responses to similar lead exposures. Data derived from this study will lead to the first gene expression database for lead toxicity and advance our understanding of the metabolic, signaling and regulatory pathways that may be disturbed by developmental lead exposure. Information on the influence of genetic background on the response to this toxin may help in development of new strategies for intervention. Specific Aim 2. Assess the extent to which different environments modify behavioral and molecular deficits associated with developmental lead exposure. These studies will examine the effects of different housing environments on lead-induced deficits in spatial learning and memory and initial candidate gene expression (i.e., neurotrophic factor and NMDA receptor subtype expression) in the hippocampus. We hypothesize that animals raised in a social but impoverished environment will have more severe deficits and that animals reared in enriched environments and that the latter will be at least partially protected against the detrimental effects of lead exposure regardless of dose or type of exposure. Our research will not only examine the role of genetics in influencing the outcome from lead exposure but may demonstrate that the effects of lead on the brain are not immutable. Early intervention with therapy based on the principles of environmental enrichment might prove useful for attenuating at least some lead-related functional deficits. The proposed research will provide new data on the role of genetics in influencing the outcome from developmental lead exposure by assessing how different types and levels of developmental lead exposure interacts with genetic variation to result in brain damage. Additionally, examination of how rearing in different environments modify behavioral and molecular deficits associated with development lead exposure may demonstrate that the effects of lead on the brain are not immutable and that early intervention with therapy based on the principles of environmental enrichment might prove useful for attenuating at least some lead-related functional deficits.